Agriculture Reference
In-Depth Information
0.12
S. portulacastrum
M. crystallinum
A
B/B
0.1
b
B/Cd
b
0.08
Cd/Cd
b
B/Cd
b
a
0.06
a
B/B
Cd/Cd
0.04
0
50
350
400
100
150
200
250
300
µg Cd/ gDW Shoots
0.12
B
S. portulacastrum
M. crystallinum
B/B
B/Ni
b
b
0.1
0.08
Ni/Ni
B/Ni
b
a
0.06
B/B
b
Ni/Ni
ab
0.04
0
20
140
40
60
80
100
120
Figure 6. Relationship between RGR (d-1) and Cd (A) or Ni (B) shoots concentrations in S.
portulacastrum and M. crystallinum. Means of 8 replicates. Statistical analysis was linked to the RGR,
Values marked with same letter are not significantly different at p= 0.05.
This hypothesis was confirmed by the experiments of Cohen
et al.
(1998) and those of
Awad and Römheld (2000) who founded that Fe-deficiency would stimulate Cd
2+
uptake
respectively by the roots of pea and wheat plants. In this context, other researches showed
that in plants, Cd
2+
was assumed to enter root cells via either the higher affinity uptake system
for Fe
2+
or low affinity system for Ca
2+
(Roosens
et al,
2003, Lombi
et al,
2002, Zhao
et al.
2002).
Our results also showed that the split-root system, ensuring an adequate Ca
2+
, K
+
and Fe
supply by one half of the root system, and a load of leaves with Cd
2+
and at a less degree with
Ni
2+
by the other root half, improved completely growth. Thus, relatively high leaf heavy
metals (Ni
2+
and Cd
2+
) contents could be compatible with an optimal growth activity when
shoots were sufficiently alimented with essential nutrients. Thus, we suggest that high Ca, K
and Fe availabilities in the medium could alleviate the toxicity induced by heavy metals and
enhance the capacity of plants to extract Cd
2+
and Ni
2+
by improving growth concomitant to a
relatively elevated Cd
2+
and Ni
2+
-shoots concentration. With respect to metals (Cd
2+
and Ni
2+
)
shoot accumulation, and since extracted metals amount depend in the same time on shoot
